Portable data collection devices are widely used in manufacturing, service and package delivery industries to perform a variety of on-site data collection activities. Such portable data collection devices often include integrated bar code dataform readers adapted to read bar code dataforms affixed to products, product packaging and/or containers in warehouses, retail stores, shipping terminals, etc. for inventory control, tracking, production control and expediting, quality assurance and other purposes. Various bar code dataform readers have been proposed for portable data collection devices including laser scanners and one dimensional (1D) charge coupled device (CCD) imaging assemblies, both of which are capable of reading 1D bar code dataforms, that is, bar codes consisting of a single row of contrasting black bars and white spaces of varying widths. Both of these readers are also capable of reading a "stacked" two dimensional (2D) bar code dataforms such as PDF417, which has row indicator patterns utilized by the reader for vertical synchronization.
A two dimensional (2D) imaging based dataform reader has been proposed in U.S. application Ser. No. 08/544,618, filed Oct. 18, 1995 and entitled "Extended Working Range Dataform Reader Including Fuzzy Logic Image Control Circuitry". The 2D dataform reader disclosed in application Ser. No. 08/544,618 which is assigned to the assignee of the present application, includes an imaging assembly having a two dimensional array of photosensor (also referred throughout as photodiodes or pixels) adapted to read 2D bar code dataforms (e.g., PDF417, Supercode, etc.) with vertical synchronization row indicator patterns as well as matrix dataforms (e.g., MaxiCode, Data Matrix, Code 1, etc.) which do not include vertical synchronization patterns. The 2D dataform reader disclosed in application Ser. No. 08/544,618 utilizes an open loop feedback control system including fuzzy logic circuitry to determine proper exposure time and gain parameters for a camera assembly.
While using a portable data collection device to sequentially read bar code dataforms affixed to products or containers in a production facility, warehouse or retail store, an operator may come upon an item which is damaged, incomplete, mislabeled, in the wrong location, etc. In such a event, it would be desirable for the operator to make a note of the problem item so that appropriate corrective action may be taken by supervisory personnel. However, requiring the operator to make a handwritten notation on a clipboard or input information concerning the item using a keyboard or keypad of the portable data collection device is both time consuming and error prone.
What is needed is a portable data collection device having a 2D imaging assembly that can be actuated to read bar code dataforms by depressing a trigger and, when a problem item is found, the imaging assembly can be actuated with a separate trigger to record an image of the problem item. This would enable "information", that is, an image of the problem item, to be recorded without seriously interrupting the normal course of the operator's work. Additionally, it would be desirable to transmit the recorded image of the problem item to appropriate supervisory personnel so that appropriate corrective action may be taken. In certain instances, it may be sufficient to record a single frame of the image of a problem item, while in other cases, for example, if the item is larger than a field of view or target area of the imaging assembly, it may be necessary to record a continuous video image of the problem item to permit the operator to record a complete view of the item. It would also be desirable to provide an audio capture module to simultaneously capture the operator's voice, enabling the operator to provide further identification and/or commentary on the problem item to aid supervisory personnel in locating the item and taking appropriate corrective action.
Furthermore, in package delivery applications, upon delivery of a package, the delivery person typically uses a portable data collection device to read a bar code dataform affixed to the delivered package. Normally, the delivery person also obtains a signature of the person receiving the package. Typically, the signature of the person receiving the package is on a sheet of paper that must be filed with the package delivery records or on a signature capture digitizer pad so that the signature may electronically filed.
What is needed is a portable collection data device having a 2D imaging assembly that can be actuated to read a bar code dataform by depressing one trigger and can be actuated by a separate trigger, or applications software, to record an image of a signature of a person receiving a package so that the signature can be filed electronically.
As an alternative to using one trigger to read a bar code dataform and using the second trigger to image an adjacent signature block with a recipient's signature included therein a single trigger could be used to decode a dataform and capture an image of the recipient's signature, the dataform could be encoded if the signature block is at a predetermined position with respect to the dataform, a signal image may include both the dataform and the signature block. What is needed is a portable data collection device that can be actuated by a single trigger to capture an image of a bar code dataform and an adjacent signature block, decode the bar code dataform, determine the position of the signature block, and output a compressed digitized representation of the portion of the image comprising the signature block for subsequent downloading to a remote device.
Furthermore, it would be desirable if the portable data collection device included a color imaging system to record a color image or series of images using a "color photosensor array." Typical "color photosensor arrays" include a red, green and blue (RGB) microfilter overlying a traditional 2D photosensor array to provide for color image data. A typical color filter for a 2D photosensor array comprises a matrix of positions overlying corresponding a pixel positions. Typically, 50% of the positions are green, 25% of the positions are red and the remaining 25% of the positions are blue. Unfortunately, the color of a filter position effects the transmittivity of light through that position and, therefore, the intensity of illumination incident on a photosensor or pixel overlied by the filter position.
The charge accumulating on a given photosensor over an exposure period is dependent on the intensity of illumination incident on that photosensor. An imaging assembly utilizing a charge coupled device to read out charges accumulated on photosensors accumulated over an exposure period convert the charges accumulated on individual photosensors to an analog voltage signal and an A/D converter converts the signal into digital gray scale values representing a frame of a captured image and stores the gray scale values in a frame buffer memory. The gray scale values of the pixels within the frame are analyzed by the imaging system to identify a dataform pattern, which is subsequently decoded by decoding circuitry of the imaging assembly.
Because a color filter differentially alters the illumination intensity incident on a photosensor depending on whether the photosensor is overlied by a red, green or blue filter position, the resulting gray scale value would also be altered. Accordingly, the addition of a color filter to a photosensor array would decrease an imaging system's ability to accurately identify and decode a dataform imaged in a captured frame image, that is, imaging in color would decrease the effective resolution of the imaging assembly, i.e., the assembly's ability to read of a dataform in a captured image frame.
What is need is portable data collection device including a color imaging system with a color filter wherein the imaging system includes compensation circuitry to compensate for the variation in light transmittivity of different colored filter positions so that a dataform in a captured image may be accurately identified and decoded by the imaging system.